[time-nuts] OT: Levelled sine wave generator

David C. Partridge david.partridge at dsl.pipex.com
Mon Dec 15 15:18:41 UTC 2008


Hi Didier,

I was actually considering an SG-504 to get the frequency range at the upper
end.    I has however hoping to better both that and the SG-503 by putting
it all in one for the complete frequency range and ideally having a better
generator as as well.

Conceptually I was hoping to aim for a capbility similar to the Tegam SG5050
(sort of like a "grown-up" version of the SG5030 but with a frequency range
extending up to 2.5GHz (I only need 1GHz though).

D.

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Didier
Sent: 15 December 2008 12:29
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] OT: Levelled sine wave generator

Dave,

You may want to look at the SG-503 Tektronix plug-in for a levelled sine
generator. It goes to 250 MHz, and the full service manual with schematics
is on my web site in the Manuals pages:

http://www.ko4bb.com/cgi-bin/manuals.pl

I have one and it works as advertised. Great for scope calibration, not so
great as a signal generator :-)

Didier KO4BB 

> -----Original Message-----
> From: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com] On Behalf Of David C. Partridge
> Sent: Monday, December 15, 2008 4:04 AM
> To: 'Discussion of precise time and frequency measurement'
> Subject: [time-nuts] OT: Levelled sine wave generator
> 
> Sort of related, but only just - however the signal to noise ratio 
> here is so good that I feel impelled to ask.
> 
> For 'scope calibration I'm considering building a levelled sine wave 
> generator.
> 
> Ideally the specs I'm looking for are:
> 
>  o Close to DC (10kHz or 100kHz would be fine) up to at least 1GHz.
>  	more would be better but not critical
> 
>  o Output levels from 0.5Vp-p(-2dBm) to at least
> 4Vp-p(+16dBm) into 50R
> 	 (up to >6Vp-p(say +20dBm) would be better)
> 
>  o Output flatness levelled within 2% of desired output level
> (+/- 0.086dB)
> 	across the entire frequency range at the final connector to the DUT
> 	This will almost certainly mean an external levelling head.
> 
>  o Modulation - not critical, FM or AM might be useful.
> 
>  o A logarithmic sweep capability might be nice, but isn't necessary.
> 
>  o Frequency display - nice to have but output to external counter is 
> OK.
> 
> Generating the basic signal is probably just a case of using something 
> like an HP VTO-8200, mixing it with 2GHz (Mini-Circuits RMS30?), low 
> pass filter, an AGC stage (see
> below) and then amplify probably using an MMIC like the Mini-Circuits 
> ERA-2SM followed by an additional stage to get the extra few
> dB.   For more accurate frequency control some sort of 
> synthesiser locked to
> a reference might be in order (I had to get a time-nuts hook in here 
> somehow).
> 
> The question is what should go in the sensor head?
> 
> Logically I need to sample a proportion of the signal delivered to the 
> output connector, compare the output of the sensor against a DC 
> reference level telling it the desired output level, and feed back a 
> voltage to a wideband AGC stage (any suggestions for this?) in the 
> main
> unit.   I also
> need to be able to detect that output is not levelled.
> 
> Or should I just forget the whole idea and go talk to R&S with a large 
> cheque in hand?
> 
> Cheers
> Dave
> 
> 
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